Tail merging can convert an undef use into a normal one when creating a
common tail. Doing so can make the register live out from a block which
previously contained the undef use. To keep the liveness up-to-date,
insert IMPLICIT_DEFs in such blocks when necessary.
To enable this patch the computeLiveIns() function which used to
compute live-ins for a block and set them immediately is split into new
functions:
- computeLiveIns() just computes the live-ins in a LivePhysRegs set.
- addLiveIns() applies the live-ins to a block live-in list.
- computeAndAddLiveIns() is a convenience function combining the other
two functions and behaving like computeLiveIns() before this patch.
Based on a patch by Krzysztof Parzyszek <kparzysz@codeaurora.org>
Differential Revision: https://reviews.llvm.org/D37034
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312668 91177308-0d34-0410-b5e6-96231b3b80d8
The conditional tail call logic did the wrong thing when both
destinations of a conditional branch were the same:
BB#1: derived from LLVM BB %entry
Live Ins: %EFLAGS
Predecessors according to CFG: BB#0
JE_1 <BB#5>, %EFLAGS<imp-use,kill>
JMP_1 <BB#5>
BB#5: derived from LLVM BB %sw.epilog
Predecessors according to CFG: BB#1
TCRETURNdi64 <ga:@mergeable_conditional_tailcall>, 0, ...
We would fold the JE_1 to a TCRETURNdi64cc, and then remove our BB#5
successor. Then BB#5 would be deleted as it had no predecessors, leaving
a dangling "JMP_1 <BB#5>" reference behind to cause assertions later.
This patch checks that both conditional branch destinations are
different before doing the transform. The standard branch folding logic
is able to remove both the JMP_1 and the JE_1, and for my test case we
end up forming a better conditional tail call later.
Fixes PR33980
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309422 91177308-0d34-0410-b5e6-96231b3b80d8
CFI instructions that set appropriate cfa offset and cfa register are now
inserted in emitEpilogue() in X86FrameLowering.
Majority of the changes in this patch:
1. Ensure that CFI instructions do not affect code generation.
2. Enable maintaining correct information about cfa offset and cfa register
in a function when basic blocks are reordered, merged, split, duplicated.
These changes are target independent and described below.
Changed CFI instructions so that they:
1. are duplicable
2. are not counted as instructions when tail duplicating or tail merging
3. can be compared as equal
Add information to each MachineBasicBlock about cfa offset and cfa register
that are valid at its entry and exit (incoming and outgoing CFI info). Add
support for updating this information when basic blocks are merged, split,
duplicated, created. Add a verification pass (CFIInfoVerifier) that checks
that outgoing cfa offset and register of predecessor blocks match incoming
values of their successors.
Incoming and outgoing CFI information is used by a late pass
(CFIInstrInserter) that corrects CFA calculation rule for a basic block if
needed. That means that additional CFI instructions get inserted at basic
block beginning to correct the rule for calculating CFA. Having CFI
instructions in function epilogue can cause incorrect CFA calculation rule
for some basic blocks. This can happen if, due to basic block reordering,
or the existence of multiple epilogue blocks, some of the blocks have wrong
cfa offset and register values set by the epilogue block above them.
Patch by Violeta Vukobrat.
Differential Revision: https://reviews.llvm.org/D18046
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306529 91177308-0d34-0410-b5e6-96231b3b80d8
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.
I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.
This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.
Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304787 91177308-0d34-0410-b5e6-96231b3b80d8
Re-commit r303937 + r303949 as they were not the cause for the build
failures.
We do not track liveness of reserved registers so adding them to the
liveins list in computeLiveIns() was completely unnecessary.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303970 91177308-0d34-0410-b5e6-96231b3b80d8
Tentatively revert, suspecting that it caused breakage in stage2
buildbots.
This reverts commit r303949.
This reverts commit r303937.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303955 91177308-0d34-0410-b5e6-96231b3b80d8
We do not track liveness of reserved registers so adding them to the
liveins list in computeLiveIns() was completely unnecessary.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303937 91177308-0d34-0410-b5e6-96231b3b80d8
Rename the DEBUG_TYPE to match the names of corresponding passes where
it makes sense. Also establish the pattern of simply referencing
DEBUG_TYPE instead of repeating the passname where possible.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303921 91177308-0d34-0410-b5e6-96231b3b80d8
Hoisting common code can cause registers that live-in in the successor
blocks to no longer be live-in. The live-in information needs to be
updated to reflect this, or otherwise incorrect code can be generated
later on.
Differential Revision: https://reviews.llvm.org/D32661
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302228 91177308-0d34-0410-b5e6-96231b3b80d8
Merging identical blocks when it doesn't reduce fallthrough. It is common for
the blocks created from critical edge splitting to be identical. We would like
to merge these blocks whenever doing so would not reduce fallthrough.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299890 91177308-0d34-0410-b5e6-96231b3b80d8
Summary: D25742 improved the precision of debug locations for PGO by removing debug locations from common tail when tail-merging. However, if identical insturctions that are merged into a common tail have the same debug locations, there's no need to remove them. This patch creates a merged debug location of identical instructions across SameTails and assign it to the instruction in the common tail, so that the debug locations are maintained if they are same across identical instructions.
Reviewers: aprantl, probinson, MatzeB, rob.lougher
Reviewed By: aprantl
Subscribers: andreadb, llvm-commits
Differential Revision: https://reviews.llvm.org/D30226
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297805 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Currently, BranchFolder drops DebugLoc for branch instructions in some places. For example, for the test code attached, the branch instruction of 'entry' block has a DILocation of
```
!12 = !DILocation(line: 6, column: 3, scope: !11)
```
, but this information is gone when then block is lowered because BranchFolder misses it. This patch is a fix for this issue.
Reviewers: qcolombet, aprantl, craig.topper, MatzeB
Reviewed By: aprantl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29902
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295684 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts r294348, which removed support for conditional tail calls
due to the PR above. It fixes the PR by marking live registers as
implicitly used and defined by the now predicated tailcall. This is
similar to how IfConversion predicates instructions.
Differential Revision: https://reviews.llvm.org/D29856
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295262 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Blocks ending in unreachable are typically cold because they end the
program or throw an exception, so merging them with other identical
blocks is usually profitable because it reduces the size of cold code.
MachineBlockPlacement generally does not arrange to fall through to such
blocks, so commoning these blocks will not introduce additional
unconditional branches.
Reviewers: hans, iteratee, haicheng
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29153
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295105 91177308-0d34-0410-b5e6-96231b3b80d8
They are currently modelled incorrectly (as calls, which clobber
registers, confusing e.g. Machine Copy Propagation).
Reverting until we figure out the proper solution.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294348 91177308-0d34-0410-b5e6-96231b3b80d8
When choosing the best successor for a block, ordinarily we would have preferred
a block that preserves the CFG unless there is a strong probability the other
direction. For small blocks that can be duplicated we now skip that requirement
as well, subject to some simple frequency calculations.
Differential Revision: https://reviews.llvm.org/D28583
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293716 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This commits moves skipDebugInstructionsForward and
skipDebugInstructionsBackward from lib/CodeGen/IfConversion.cpp
to include/llvm/CodeGen/MachineBasicBlock.h and updates
some codgen files to use them.
This refactoring was suggested in https://reviews.llvm.org/D27688
and I thought it's best to do the refactoring in a separate
review, but I could also put both changes in a single review
if that's preferred.
Also, the names for the functions aren't the snappiest and
I would be happy to rename them if anybody has suggestions.
Reviewers: eli.friedman, iteratee, aprantl, MatzeB
Subscribers: MatzeB, llvm-commits
Differential Revision: https://reviews.llvm.org/D27782
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289933 91177308-0d34-0410-b5e6-96231b3b80d8
This reapplies revision 285093. Original commit message:
The branch folding pass tail merges blocks into a common-tail. However, the
tail retains the debug information from one of the original inputs to the
merge (chosen randomly). This is a problem for sampled-based PGO, as hits
on the common-tail will be attributed to whichever block was chosen,
irrespective of which path was actually taken to the common-tail.
This patch fixes the issue by nulling the debug location for the common-tail.
Differential Revision: https://reviews.llvm.org/D25742
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285212 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts r285093, as it caused unexpected buildbot failures on
clang-ppc64le-linux, clang-ppc64be-linux, clang-ppc64be-linux-multistage
and clang-ppc64be-linux-lnt. Failing test ubsan/TestCases/TypeCheck/vptr.cpp.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285110 91177308-0d34-0410-b5e6-96231b3b80d8
The branch folding pass tail merges blocks into a common-tail. However, the
tail retains the debug information from one of the original inputs to the
merge (chosen randomly). This is a problem for sampled-based PGO, as hits
on the common-tail will be attributed to whichever block was chosen,
irrespective of which path was actually taken to the common-tail.
This patch fixes the issue by nulling the debug location for the common-tail.
Differential Revision: https://reviews.llvm.org/D25742
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285093 91177308-0d34-0410-b5e6-96231b3b80d8
Branch folder removes implicit defs if they are the only non-branching
instructions in a block, and the branches do not use the defined registers.
The problem is that in some cases these implicit defs are required for
the liveness information to be correct.
Differential Revision: https://reviews.llvm.org/D25478
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284036 91177308-0d34-0410-b5e6-96231b3b80d8
When branching to a block that immediately tail calls, it is possible to fold
the call directly into the branch if the call is direct and there is no stack
adjustment, saving one byte.
Example:
define void @f(i32 %x, i32 %y) {
entry:
%p = icmp eq i32 %x, %y
br i1 %p, label %bb1, label %bb2
bb1:
tail call void @foo()
ret void
bb2:
tail call void @bar()
ret void
}
before:
f:
movl 4(%esp), %eax
cmpl 8(%esp), %eax
jne .LBB0_2
jmp foo
.LBB0_2:
jmp bar
after:
f:
movl 4(%esp), %eax
cmpl 8(%esp), %eax
jne bar
.LBB0_1:
jmp foo
I don't expect any significant size savings from this (on a Clang bootstrap I
saw 288 bytes), but it does make the code a little tighter.
This patch only does 32-bit, but 64-bit would work similarly.
Differential Revision: https://reviews.llvm.org/D24108
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280832 91177308-0d34-0410-b5e6-96231b3b80d8
This is prep work for allowing the threshold to be different during layout,
and to enforce a single threshold between merging and duplicating during
layout. No observable change intended.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279117 91177308-0d34-0410-b5e6-96231b3b80d8
Fixed a bug in the test case.
To fix PR28104, this patch restricts tail merging to blocks that belong to the
same loop after MBP.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278575 91177308-0d34-0410-b5e6-96231b3b80d8
This change makes it possible for tail-duplication and tail-merging to
be disjoint. By being less aggressive when merging during layout, there are no
overlapping cases between tail-duplication and tail-merging, provided the
thresholds are disjoint.
There is a remaining TODO to benchmark the succ_size() test for non-layout tail
merging.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278265 91177308-0d34-0410-b5e6-96231b3b80d8
Use LivePhysRegs with a backwards walking algorithm to update live in
lists, this way the results do not depend on the presence of kill flags
anymore.
This patch also reduces the number of registers added as live-in.
Previously all pristine registers as well as all sub registers of a
super register were added resulting in unnecessarily large live in
lists. This fixed https://llvm.org/PR25263.
Differential Revision: http://reviews.llvm.org/D22027
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275201 91177308-0d34-0410-b5e6-96231b3b80d8
Blocks to be tail-merged may share more than one successor. Correct the
comment to state that they share a specific successor, SuccBB, rather
than a single successor, which is not true.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275104 91177308-0d34-0410-b5e6-96231b3b80d8
Tail merge was making the assumption that a layout successor or
predecessor was always a cfg successor/predecessor. Remove that
assumption. Changes to tests are necessary because the errant cfg edges
were preventing optimizations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273700 91177308-0d34-0410-b5e6-96231b3b80d8
This reapplies commit r271930, r271915, r271923. They hit a bug in
Thumb which is fixed in r272258 now.
The original message:
The code layout that TailMerging (inside BranchFolding) works on is not the
final layout optimized based on the branch probability. Generally, after
BlockPlacement, many new merging opportunities emerge.
This patch calls Tail Merging after MBP and calls MBP again if Tail Merging
merges anything.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272267 91177308-0d34-0410-b5e6-96231b3b80d8
The code layout that TailMerging (inside BranchFolding) works on is not the
final layout optimized based on the branch probability. Generally, after
BlockPlacement, many new merging opportunities emerge.
This patch calls Tail Merging after MBP and calls MBP again if Tail Merging
merges anything.
Differential Revision: http://reviews.llvm.org/D20276
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@271925 91177308-0d34-0410-b5e6-96231b3b80d8
Move the register stackification and coloring passes to run very late, after
PEI, tail duplication, and most other passes. This means that all code emitted
and expanded by those passes is now exposed to these passes. This also
eliminates the need for prologue/epilogue code to be manually stackified,
which significantly simplifies the code.
This does require running LiveIntervals a second time. It's useful to think
of these late passes not as late optimization passes, but as a domain-specific
compression algorithm based on knowledge of liveness information. It's used to
compress the code after all conventional optimizations are complete, which is
why it uses LiveIntervals at a phase when actual optimization passes don't
typically need it.
Differential Revision: http://reviews.llvm.org/D20075
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@269012 91177308-0d34-0410-b5e6-96231b3b80d8
